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Date: Sat, 30 Apr 2011 18:34:18 +0200
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To: Reindl Harald <h.reindl@thelounge.net>
Cc: internals@lists.php.net
Content-Type: multipart/alternative; boundary=0016364163149eba0d04a2255cd6
Subject: Re: [PHP-DEV] Change Request: Make PDO default to not emulate
 prepared statements for MySQL
From: info@tyrael.hu (Ferenc Kovacs)

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On Sat, Apr 30, 2011 at 6:02 PM, Reindl Harald <h.reindl@thelounge.net>wrote:

>
> Am 30.04.2011 17:45, schrieb Ferenc Kovacs:
> > On Sat, Apr 30, 2011 at 5:39 PM, Rasmus Lerdorf <rasmus@lerdorf.com>
> wrote:
> >> Do you realize why we did this in the first place? The common versions
> of
> >> MySQL in use out there are not very clever when it comes to the native
> >> prepared statement handling. First, there is no prepared statement
> cache, so
> >> there is no benefit to doing them natively, but worse, when you use a
> native
> >> prepared statement you completely miss the query result cache. As a
> result
> >> emulated prepared statements are either the same speed or faster than
> the
> >> native ones. Changing this default would result in a performance hit for
> >> most people. It should be better documented, but that is the only
> problem I
> >> see here.
> >>
> > I disable query_cache on my machines, because it can cause performance
> and
> > stability issues.
> >
> http://www.mysqlperformanceblog.com/2011/04/10/should-we-give-a-mysqlquery-cache-a-second-chance/
>
> i guess you must have some really strange things in your applications
>
>
not really.
but the global mutex and the coarse invalidation makes it capable of
stalling a server and it wasn't easy so spot that.
at least with vanilla mysql 5.1
http://www.xaprb.com/blog/2010/09/15/making-query-cache-contention-more-obvious/
http://bugs.mysql.com/bug.php?id=56822

but this is offtopic here, I shouldn't have brought this up.

Tyrael

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